Technical Field
The present disclosure relates to a motor driving controller.
Background Art
In a general motor driven by switching energization to a coil, an electromagnetic vibration component by energization switching is one of main factors, which worsen vibrations, and some countermeasures need to be taken. In a motor with a use rotation speed determined, resonance can be avoided in the manner of rotation at the use rotation speed for avoiding resonance. However, for example, like an axial fan motor, in a motor where a vibration peak value at all the rotation speeds from a halt to a maximum rotation speed has to be equal to or lower than a fixed value, the above-mentioned method for avoiding resonance cannot be used and it is troublesome to conceive of a countermeasure.
Japanese Unexamined Patent Application Publication No. 2011-55651 describes a motor controller for restricting occurrence of noises based on vibrations of a stator due to resonance at a natural frequency of a motor. The motor controller described in Japanese Unexamined Patent Application Publication No. 2011-55651 comprises a rotation speed calculation part for calculating a rotation speed of a rotor and a modulation rate adjustment part for adjusting a modulation rate to an inverter on the basis of a rotation speed calculated by the rotation speed calculation part and the natural frequency of the stator. This motor controller prevents occurrence of a resonance phenomenon caused by a frequency of a harmonic component and a natural frequency F of the stator, thereby to restrict occurrence of noises due to vibrations of the stator.
The motor controller described in Japanese Unexamined Patent Application Publication No. 2011-55651 needs to adjust a modulation ratio to an inverter at every frequency of a PWM (Pulse Width Modulation) signal, as in 180-degrees conduction. Due to this, the following problem has occurred. Namely, a microcomputer with high processing capability is needed and therefore, the costs increase.
The present disclosure is related to providing a motor driving controller, which can evade resonance at a natural frequency of a motor occurring in a predetermined rotation speed range, while the motor driving controller is configured to be inexpensive.